Transformer



May 30, 1950 c. F, FREY, JR 2,509,427

TRANSFORMER Filed Aug. 28, 1946` INVENTOR ATTORNEY Patented May 30, 1950 TRANsFoRMER Cleon F. Frey, Jr., Greenfield, Ind., assignor to P. R. Mallory & Co., Inc., Indianapolis, Ind., a

corporation of Delaware Application August 28, 1946, Serial No. 693,546

Claims.

This invention relates to transformers and, more particularly, to intermediate frequency transformers utilizing a core of pressed, powdered paramagnetic material.

Heretofore, conventional intermediate frequency transformers have ordinarily consisted of a can having a pair of coils mounted therein on an axially-extending insulating rod. With such a construction, it is necessary that the coils be spaced a considerable distance apart in order to obtain the rather loose coupling therebetween which is desired for intermediate frequency circuits. Furthermore, a pair of coils separated by a dielectric material such as air or an insulating rod have substantial exterior fields which necessitates spacing the shield can a considerable distance from the coils in order to minimize inductive losses. As a result of these factors, the conventional intermediate frequency transformer together with its trimmer condensers has occupied considerable space upon the chassis of the radio set which is undesirable in view of the modern tendency toward utilizing smaller sets together with circuit components of the minimum size therefor. As a further result of this construction, the adjustment of the coils to obtain the proper coupling is quite critical and difficult. These difficulties are accentuated by the fact that the top portion or peak of the resonance curve for the intermediate frequency transformer should be sufficiently broad to cover the entire audible range of frequencies, but, nevertheless, the resonance peak should be sufficiently narrow to provide a, high degree of selectivity for the receiver. It will be appreciated, therefore, that critical adjustments are required to obtain proper resonance characteristics in the intermediate frequency portion of a superheterodyne circuit.

It is an object of this invention to provide a transformer of small size which will adequately fulfill the requirements of intermediate frequency circuits.

It is a further object of the invention to provide an intermediate frequency transformer which is readily adjustable to obtain the desired coupling between the coils and in which, after adjustment, the coupling is accurately maintained at its adjusted value.

It is a still further object of the invention to provide an intermediate frequency transformer having an efficient closed magnetic flux path for each coil with resultant elimination of stray fields.

It is a still further object of the invention t0 provide a transformer of simple and economical construction which will operate reliably for long periods of time.

Other objects of the invention will be apparent from the following description and accompanying drawings taken in connection with the appended claims.

The invention accordingly comprises the features of construction, combination of elements, arrangement of parts, and methods of manufacture referred to above or which will be brought out and exemplified in the disclosure hereinafter set forth, including the illustrations in the drawings, the scope of the invention being indicated in the appended claims.

For a fuller understandingof the nature and objects of the invention as well as for specific fulfillment thereof, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:

Figure 1 is a vertical, sectional view, partially in elevation, of the novel intermediate frequency transformer;

Figures 2, 3 and 4 are, respectively, sectional views taken along the lines 2 2, 3-3 and 4-4 of Figure 1;

Figure 5 is a perspective View of the core;

Figure 6 is a schematic circuit diagram illustrating a, feature of the invention; and

Figure 7 is a vertical, sectional view showing a modified core construction.

While a preferred embodiment of the invention is described herein, it is contemplated that con- Siderable variation may be made in the method of procedure and the construction of parts without departing from the spirit of the invention. In the following description and in the claims, parts will be identified by specic names for convenience, but they are intended to be as generic in their application to similar parts as the art will permit.

Referring to the drawings in detail, and particularly to Figures 1 and 2, the transformer comprises a cylindrical shell I0 of pressed, powdered paramagnetic material. Mounted within the shell I0 are a pair of coil units Il, I2 which are separated by a. spacer I3 of insulating material. Each coil unit includes a core I4 which comprises a generally cylindrical body I5. Figure 5, having longitudinal slots or grooves I6 formed therein which, preferably, extend along diametrically opposite surfaces of the core. The adjacent ends of the slots I6 are connected by end grooves or slots Il which, preferably, extend asomar diametrically of the core structure i5. A pair oi' coils I8 and iii are wound in the respective sets of slots formed in the cores so that the outer surfaces of each coil are iiush with the periphery of the associated core as is clearly indicated in Figures 2 and 4. The coil units II, i2 may be of identical construction and, in the example shown, the windings have the same number of turns.

Referring now to Figures 1 and 4, it will be seen that the shell iii is enclosed by a support which consists of a base 20 of insulating material together with an insulating casing 2i, this support being of generally rectangular cross section and holding the shell I@ and other parts to be described later. The insulating support, in turn, is enclosed by a metal shield, preferably of aluminum, which is formed by a base 22 and a casing 23. It will be observed that the base is anged as at 24 to form an integral rigid container for holding the parts which make up theintermediate frequency transformer.

A pair of trimmer condensers 25, 25 ofxconventional design are mounted within the casing at the respective opposite ends of the shell I I) and the casing is suitably apertured to permit mounting of the trimmer condensers and access to the respective adjusting screws 2l thereon. 'I'he trimmer condenser plates, not shown, are connected to lugs 28, which, in turn, are connected in circuit with the coils by conductors 29 in such fashion that the trimmer condenser 25 is connected in parallel with the coil i8 and the trimmer condenser 26 is connected in parallel with the coil I9. Conductors 32 are also attached to the lugs 28, these conductors extending through suitable apertures in the casing and through the interspace between the shell Iii and the casing for connection to an external circuit.

It will be apparent from an inspection of Figure 1 that each of the cores ibi defines a closed magnetic path with the shell Iii, such closed magnetic paths extending, respectively, around the coils or windings I8, I9. In this manner, the external field of the coils is substantially minimized or even eliminated so that the shield can may be placed directly in contact with the outer surface of the shell I or spaced therefrom a short distance as by the insulating members 2li, 2i. Moreover, theparamagnetic core structure results in a closed magnetic circuit oi very low losses which insures efiicient operation of the transformer.

In adjusting the transformer, coil units II and I2 are rotated relative to each other to thereby change the coupling between the windings I8 and I9. Although this adjustment is cuite critical, as heretofore pointed out, the coupling may be accurately and conveniently accomplished by such rotation of the coil units. Thereupon, the coil units are iixed in position, as by bodies of wax or other sealing compound, as indicated at 33.

As a result, the desired coupling is accurately` maintained throughout the life of the transformer while, at the same time, a transformer of small dimensions which is very eflicient in operation is obtained.

A modiiied form of core construction is shown in Figure '7. Since many parts of this modified core construction are similar to those already described, like parts will be indicated by corresponding reference characters. The core IIJ of Figure I is directly in contact with an outer cylindrical metallic shield can 35. Mounted Within the core are a pair of coil units 36, 31 and each o1' these coil units comprises a cylindrical core 38 having a circumferential slot Sii formed therein. Each slot carries a winding liti, the our surface oi which is ush with the outer surface oi the core. The connections or terminal wires ior the .windings extend through slots Iii formed in the respective cores and these leads are connected to trimmer condensers, not shown, in the manner illustrated by Figure 6. In utilizing the modified core construction, the adjustment of the coupling between the coils is effected by longitudinal relative movement of the cores within the shell I0 rather than rotation thereof. When the desired coupling is obtained, the core units are permanently iixed in place by bodies of wax or other suitable compound, as shown at 42. It will be apparent that the desired coupling between the windings can be readily attained and accurately maintained after the position of the cores has been adjusted.

While the present invention, as to its objects and advantages, has been described herein as carried out in specific embodiments thereof, it is not desired to be limited thereby but it is intended to cover the invention broadly within the spirit and scope of the appended claims. Thus, for example, although I prefer to use iron for the material for the core units, the invention also embraces the use of other paramagnetic materials. Further, although the shell Iii has been shown as a cylindrical shell, it is within the purview of the invention to utilize a square, oblong or other cross section for the shell.

What is claimed as new and desired to be secured by Letters Patent is:

1. In an iron core intermediate frequency transformer, a cylindrical shell of pressed, powdered iron. a pair of coil units mounted in said shell in direct contact therewith, each of said units comprising a core of pressed powdered iron and a winding on said core, said units being rotatable relative to each other, within said shell to a predetermined angular relationship between said windings. and means for xing said units in said angular relationship within the shell.

2. In an intermediate frequency transformer; a pair of coil units each comprising an elongated core of pressed, powdered, paramagnetic material having a pair o1' longitudinally-extending grooves, the adjacent ends of said grooves being connected by end grooved portions, and a winding supported in said grooves, the outer surface oi' said winding being flush with the outer surface of said core; and a supporting structure of pressed, powdered, paramagnetic material enclosing said coil units along their longitudinal axes, said coil units being Vslidably displaceable within said structure.

3. In a transformer, a hollow structure of pressed, powdered paramagnetic material, a pair of coil units mounted within said structure, the exterior of said coil units-being contiguous with the interior surface of said structure, each of said coil units comprising a core of pressed, powdered paramagnetic material and a winding on said core, and dielectric means separating said coil units, said coil units being rotatable, relative to each other. within said structure for varying the coupling between said windings.

4. A transformer structure comprising a shell of pressed, powdered paramagnetic material having a generally cylindrical inner surface, a pair of coil units mounted within said shell, each of said coil units comprising a. generally cylindrical inner core of pressed, powdered paramagnetic v material, said inner core having a pair of longiparallel planes, are rotatably adjustable, relative to each other, for varying the angular relationship between said coil units whereby the coupling is varied.

CLEON F. FREY, JR.

REFERENCES CITED The following references are of record in the me of this patent:

UNITED STATES PATENTS Number Number Name Date Chylinski Sept. 6, 1927 Smith Apr. 9, 1929 Crossley Mar. 24, 1936 Vogt Dec. 15, 1936 Neighbors June 1, 1937 Sear Mar. 29, 1938 Schaper May 16, 1939 Mennerich et al. Oct. 31, 1939 Harvey Nov. 21, 1939 Harbey Dec. 5, 1944 Berg Sept. 17, 1946 Warshaw Mar. 11, 1947 Conrad et al Nov. 11, 1947 FOREIGN PATENTS Country Date Great Britain Sept. 10, 1925 Great Britain Mar. 15, 1939 Australia Feb. 6, 1935 Australia July 30, 1942 

